1. Field of the Invention
The present invention relates to a laminate type evaporator for an air conditioner.
2. Description of the Related Art
FIG. 9 is a perspective view showing the refrigerant flow passage construction of a conventional laminate type evaporator, FIG. 10 is a plan view of a flat tube used in a laminate type evaporator that constitutes a refrigerant pipe through which refrigerant is passed, and FIG. 11 is an exploded perspective view of the flat tube.
In the laminate type evaporator 1 shown in FIG. 9, a large number of flat tubes 2 as shown in FIG. 10 are arranged in parallel at intervals, and corrugate fins (not shown) are provided between the adjacent flat tubes 2, whereby the flat tubes 2 and the corrugate fins are alternately laminated together; in the laminated state, these components are integrally brazed to each other.
As shown in FIG. 11, each flat tube 2 is composed of a pair of press-molded plates 2a and 2b with their ends being deep-drawn; the pair of plates are opposed and joined to each other. At the top end of the flat tube, there are formed in parallel a first upper tank portion 31 and a second upper tank portion 32 constituting an inlet side or an outlet side for refrigerant. At the lower end of the flat tube, there are formed in parallel a first lower tank portion 41 and a second lower tank portion 42 constituting the inlet side or the outlet side for refrigerant.
These tank portions are formed by joining together the molded plates 2a and 2b opposed to each other. That is, the first upper tank portion 31 is formed by joining together a tank forming portion 31a of the molded plate 2a and a tank forming portion 31b of the molded plate 2b, and the second upper tank portion 32 is formed by joining together a tank forming portion 32a of the molded plate 2a and a tank forming portion 32b of the molded plate 2b. Further, the first lower tank portion 41 is formed by joining together a tank forming portion 41a of the molded plate 2a and a tank forming portion 41b of the molded plate 2b, and the second lower tank portion 42 is formed by joining together a tank forming portion 42a of the molded plate 2a and a tank forming portion 42b of the molded plate 2b. 
From the portion between the first upper tank portion 31 and the second upper tank portion 32 to the portion between the first lower tank portion 41 and the second lower tank portion 42, there extends a partition 6, which is formed by joining together the bottom surfaces of a partition groove 6a of the molded plate 2a and a partition groove 6b of the molded plate 2b. By this partition 6, there are defined two flow passages through which refrigerant flows: a first refrigerant flow passage 51 and a second refrigerant flow passage 52. The first refrigerant flow passage 51 is a linear flow passage connecting the first upper tank portion 31 and the first lower tank portion 41; it is formed between a refrigerant flow passage forming portion 51a of the molded plate 2a and a refrigerant flow passage forming portion 51b of the molded plate 2b. Further, the second refrigerant flow passage 52 is a linear flow passage connecting the second upper tank portion 32 and the second lower tank portion 42; it is formed between a refrigerant flow passage forming portion 52a of the molded plate 2a and a refrigerant flow passage forming portion 52b of the molded plate 2b. 
In this way, the laminate type evaporator 1 is formed by alternately laminating together a large number of flat tubes 2 and corrugate fins. Further, as shown in FIG. 9, a side refrigerant passage 3 is provided at one refrigerant inlet/outlet side surface portion 1F of the laminated flat tubes 2. Further, a side refrigerant passage 4 is provided at the other side surface portion 1B. At the position of the side refrigerant passage 3 in the vicinity of the first upper tank portion 31, there is provided a refrigerant inlet Rin through which refrigerant flows into the laminate type evaporator 1. Further, at the position of the side refrigerant passage 3 in the vicinity of the second upper tank portion 32, there is provided adjacent to the refrigerant inlet Rin a refrigerant outlet Rout through which refrigerant flows out of the laminate type evaporator 1. The side refrigerant passage 3 communicates with the refrigerant inlet Rin and the first lower tank portion 41 of that flat tube 2 out of the laminated flat tubes 2, which is nearest to the side refrigerant passage 3 side.
Further, in the middle portion with respect to the laminating direction of the first lower tank portion 41 of the laminated flat tubes 2, there is provided a partition portion 18. Here, the partition portion 18 is formed such that no refrigerant communicates between the lower tank portions 41 of the adjacent flat tubes 2 with the partition portion 18 therebetween. In the middle portion of the second upper tank portion 32 of the laminated flat tubes 2, there is provided a partition portion 19. The partition portion 19 is formed such that no refrigerant communicates between the second upper tank portions 32 of the adjacent flat tubes 2 with the partition portion 19 therebetween.
In this way, the partition portions 18 and 19 respectively divide the first lower tank portions 41 and the second upper tank portions 32 laminated together such that the ratio of the number n2 of flat tubes on the refrigerant inlet/outlet side surface portion 1F side to the number n1 of flat tubes on the opposite side, i.e., on the side surface portion 1B side, is substantially 1:1.
Of the first refrigerant passages 51 of the flat tubes 2 laminated together and the first upper tank portions 31 and the first lower tank portions 41 at the ends thereof, those situated on the side refrigerant passage 3 side with respect to the partition portion 18 constitute a first block B1 in which refrigerant flows as refrigerant flow R1 from the first lower tank portions 41 to the first upper tank portions 31. Of the first refrigerant passages 51 of the flat tubes 2 laminated together and the first upper tank portions 31 and the first lower tank portions 41 at the ends thereof, those situated on the side refrigerant passage 4 side with respect to the partition portion 18 constitute a second block B2 in which refrigerant flows as refrigerant flow R2 from the first upper tank portions 31 to the first lower tank portions 41.
Further, of the second refrigerant passages 52 of the flat tubes 2 laminated together and the second upper tank portions 32 and the second lower tank portions 42 at the ends thereof, those situated on the side refrigerant passage 4 side with respect to the partition portion 19 constitute a third block B3 in which refrigerant flows as refrigerant flow R3 from the second upper tank portions 32 to the second lower tank portions 42. Of the second refrigerant passages 52 of the flat tubes 2 laminated together and the second upper tank portions 32 and the second lower tank portions 42 at the ends thereof, those situated on the side refrigerant passage 3 side with respect to the partition portion 19 constitute a fourth block B4 in which refrigerant flows as refrigerant flow R4 from the second lower tank portions 42 to the second upper tank portions 32.
In the laminate type evaporator 1, constructed as described above, refrigerant flowing in through the refrigerant inlet Rin passes through the side refrigerant passage 3 as a refrigerant flow RSA, and enters an inlet side tank portion 10 consisting of the first lower tank portions 41 in the first block B1. Next, it flows through the first refrigerant passages 51 of the first block B1 as refrigerant flow R1, and enters an outlet side tank portion 11 consisting of the first upper tank portions 31 in the first block B1. The refrigerant that has flowed into the outlet side tank portion 11 of the first block enters an inlet side tank portion 12 consisting of the first upper tank portions 31 in the second block B2, and flows through the first refrigerant passages 51 of the second block B2 as refrigerant flow R2 before entering an outlet side tank portion 13 consisting of the first lower tank portions 41 in the second block B2. Thereafter, the refrigerant passes through the side refrigerant passage 4 as refrigerant flow RSB, and enters an inlet side tank portion 14 consisting of the second upper tank portions 32 in the third block B3. The refrigerant that has flowed into the inlet side tank portion 14 flows through the second refrigerant passages 52 of the third block B3 as refrigerant flow R3, and enters an outlet side tank portion 15 consisting of the second lower tank portions 42 in the third block B3. The refrigerant that has flowed into the outlet side tank portion 15 enters an inlet side tank portion 16 consisting of the second lower tank portions 42 in the fourth block B4, and flows through the second refrigerant passages 52 of the fourth block B4 as refrigerant flow R4 before entering an outlet side tank portion 17 consisting of the second upper tank portions 32 in the fourth block B4. Thereafter, it flows out from the refrigerant outlet Rout connected to the outlet side tank portion 17.
However, in the laminate type evaporator 1 constructed as described above, when reducing the width of the flat tubes 2 corresponding to the flow direction 100 shown in FIG. 9 to reduce the width of the core formed by laminating together the flat tubes 2 and the corrugate fins in order to achieve a reduction in size and cost, the flow passage sectional areas of the first refrigerant flow passages 51 and the second refrigerant flow passages in the flat tubes 2 are reduced due to the division of the refrigerant flow passages of the flat tubes 2 into four blocks. When the flow passage sectional area is reduced, the refrigerant pressure loss in the flat tubes 2 increases, so that the refrigerant pressure loss of the laminate type evaporator 1 increases, resulting in a deterioration in performance in refrigeration cycle operation.
The present invention has been made with a view toward solving the above problem in the prior art. It is an object of the present invention to provide a laminate type evaporator in which the refrigerant tubes are reduced in width while reducing the refrigerant pressure loss of the laminate type evaporator, thereby making it possible to achieve a reduction in size and cost.
According to the present invention, there is provided a laminate type evaporator in which a large number of refrigerant tubes including at least a pair of first and second refrigerant flow passages are laminated together, the laminate type evaporator characterized by comprising: a refrigerant tube group in which a pair of first and second upper tank portions are respectively arranged at one end of the first and second refrigerant flow passages and in which a pair of first and second lower tank portions are respectively arranged at the other end of the first and second flow passages; a refrigerant inlet arranged on the first upper tank portion side of the refrigerant tube at one end of the refrigerant tube group; a refrigerant outlet arranged on the second upper tank portion side of the refrigerant tube at said one end; a first side refrigerant passage communicating the refrigerant inlet with the first lower tank portion of the refrigerant tube at said one end; a second side refrigerant passage communicating the first upper tank portion with the second upper tank portion of the refrigerant tube at the other end of the refrigerant tube group; a third side refrigerant passage communicating the first lower tank portion with the second lower tank portion of the refrigerant tube at said other end; a first partition portion arranged in the first lower tank portions of the refrigerant tube group; and a second partition portion arranged in the second upper tank portions of the refrigerant tube group, and the laminate type evaporator characterized in that the first partition portion and the second partition portion are arranged such that they divide the refrigerant tube group into three refrigerant flow passage groups sequentially circulating refrigerant introduced from the refrigerant inlet from the first lower tank portion of the refrigerant tube at said one end to the second upper tank portion of the refrigerant tube at said one end.